FIGS. 11A and 11B show an example of prior art analytical instrument. The analytical instrument includes a substrate 90 and a cover 91 stacked and bonded together to define a capillary 92. The capillary 92 is defined by closing an upper opening of a groove 92a formed at an upper surface of the substrate 90 by the cover 91. In the analytical instrument, when a sample in a liquid state is supplied to a sample introduction port 93 formed in the cover 91, the sample travels through the capillary 92 in a direction indicated by the arrow Na by capillary action. While the sample travels through the capillary 92, the sample may be mixed with a reagent for causing a predetermined reaction or subjected to component separation, whereby the sample is analyzed.
Conventionally, the substrate 90 and the cover 91 have sometimes been made of glass or silicone. In such a case, the substrate 90 and the cover 91 can be reliably bonded together by water glass bonding or anode bonding, for example. However, since the working of glass or silicone is not easy, the cost for manufacturing the analytical instrument disadvantageously increases.
In recent years, therefore, the substrate 90 and the cover 91 are often made of a synthetic resin for decreasing the cost for the parts. In such a case, the substrate 90 and the cover 91 are often bonded together with an adhesive or by fusing utilizing ultrasonic wave.
However, such a prior art structure has the following problems.
First, it is difficult to form a capillary 92 of an intended size. As shown in FIG. 12, when the substrate 90 and the cover 91 are bonded together with an adhesive 80, the vertical dimension H of the capillary 92 (the dimension in the thickness direction of the analytical instrument) becomes the total dimension of the depth h1 of the groove 92a and the thickness h2 of the adhesive 80. However, it is difficult to apply the adhesive 80 uniformly into a predetermined thickness. Therefore, due to the variation of the thickness of the adhesive 80, the capillary 92 having an intended vertical dimension sometimes cannot be formed. In the case where ultrasonic wave is utilized, a projection in the form of a rib (not shown) is formed at a bonding surface, and ultrasonic wave is applied to the projection to heat and deform the projection. At this time, the portion to be deformed vibrates at an amplitude of about 10 μm. Due to such vibration, the degree of deformation of the projection cannot be kept constant, so that the capillary 92 of an intended size may not be formed. When the size of the capillary 92 differs from an intended, proper one, conditions such as the travel speed or amount of the sample which flows through the capillary 92 may differ from the intended conditions, which may cause inaccurate analysis results.
Secondly, the manufacturing of the analytical instrument is difficult when the configuration of the capillary 92 is complicated. In applying the adhesive 80 to the substrate 90, the groove 92a need be avoided so that the adhesive 80 does not enter the groove 92a. Therefore, when the configuration of the capillary 92 is complicated, the application of the adhesive following the configuration is troublesome and difficult. When ultrasonic wave is utilized, the projection for fusing need be formed correspondingly to the configuration of the capillary 92. Therefore, in such a case again, the work is troublesome when the configuration of the capillary 92 is complicated.
Thirdly, the sealing performance around the capillary 92 is not good. For example, when the adhesive is not applied to a portion of the edge of the groove 92a in applying the adhesive 80 to the substrate 90, the portion forms a gap communicating with the capillary 92, causing a fear that the sample may unduly enter the portion. Such a fear exists also when ultrasonic wave is utilized. Particularly when the substrate 90 and the cover 91 are molded of resin, these members are sometimes warped to reduce the flatness at the bonding surfaces. In such a case, the sealing performance around the capillary 92 is further deteriorated.
In recent years, studies are performed to reduce the size of an entire chemical analysis system by reducing the size of the structural parts of the system and integrating the parts. When the size of the chemical analysis system is reduced, the price of the system can be reduced. Further, since the analysis can be performed by using a smaller amount of sample, it is possible to reduce the time required for the analysis, the power consumption for actuating the system, and the amount of liquid wasted after the analysis. To reduce the size of the analytical instrument to follow the downsizing trend of the chemical analysis system, a considerably small capillary 92 having a precisely intended size need be formed. However, it is difficult to meet such need when the substrate 90 and the cover 91 are bonded together with an adhesive or by utilizing ultrasonic wave.